The invention relates to an open-end wrench having a fixed clamping jaw that is rigidly connected to a wrench handle and a spring-loaded moveable clamping jaw whereby said moveable clamping jaw is pivotably mounted at a pivot point on the fixed clamping jaw and whereby said pivot point is disposed approximately at a right angle or at an angle of less than 90xc2x0 behind the rear end of the clamping surface of the moveable clamping jaw.
One-piece open-end wrenches with two jaws, which are rigidly joined with one another, have the advantage, compared to wrenches having jaws that move relatively to one another, that sufficient torque may be transferred since the mouth of the wrench sufficiently embraces the workpiece, e.g. a bolt head or a nut. The access to the workpiece is ergonomically favorable especially since the wrench handle extends from the middle of the wrench head. The hand can therefore be moved forward up to the wrench head to guide the open-end wrench during placement (on the workpiece) by touch or to conduct a necessary manipulation of the workpiece, for example, to hold a nut that rotates easily. The open-end wrench may be slipped on or removed without hitting neighboring components.
However, rigid open-end wrenches have several disadvantages. For instance, the open-end wrench has to be pulled off and slipped on again after each turning sequence. If there is only a 30xc2x0 movement possible for one turning sequence, then the open-end wrench has to be additionally turned around. This causes a considerable additional expenditure in time.
The widening of the wrench head caused by strain on the wrench head may lead to hazardous conditions. This applies particularly when the tolerances of the wrench width are added to the tolerances of the workpiece. Rigid open-end wrenches may be employed only for one nominal width and cannot be fitted to the tolerances of the workpiece. Rounded-off corners of the workpiece and misuse of nominal metric or widths in inches that are close in measurement lead also to the danger that the wrench may slip off the workpiece, which in turn leads to an increased risk of an accident. Even if a metric width or a width in inches is close, there are special rigid open-end wrenches necessary whereby the assortment of sizes is increased.
Since rigid open-end wrenches are not self-clamping, they can slip more easily in the direction of the rotating axis of the workpiece whereby the risk of an accident is increased as well. There is the lack of the possibility of adjustment to the dimensions of the workpiece, whereas it is made possible with a self-clamping action. There is also the lack of the possibility of adjustment to the operational process; for instance, the open-end wrench may not be left on the workpiece in a self-clamping position while intermediate operational steps are to be performed, or while working overhead.
The here referenced wrenches are to maintain the advantages of the open-end wrenches, avoid their disadvantages, and provide additional advantages. Particularly, it should be possible (but not absolutely necessary) to select a shape that is similar to a rigid open-end wrench. The wrench should be able to work in a ratcheting action in sequences of 30xc2x0 and should be self-clamping.
Even though there are open-end wrenches known in many different configurations, none of them fulfill all the above-mentioned requirements.
Open-end wrenches with two moveable clamping jaws (U.S. Pat. No. 4,584,913) are of relatively complicated construction and are therefore costly to manufacture and they malfunction easily. In another version of an open-end wrench (CH-A 365 348) there occurs mutual locking of the two clamping jaws by swiveling the handle, which is connected to one of the clamping jaws by a joint. The construction is here also relatively complicated and therefore is malfunctions easily; manipulation requires a lot of space for the swiveling movement of the handle.
The guiding of the moveable clamping jaw on an arch (U.S. Pat. No. 5,287,777) causes very high demands in manufacturing and also causes malfunction through build-up of dirt and wear.
On a known wrench (U.S. Pat. No. 2,907,243), the moveable clamping jaw is moved longitudinally against the force of a spring on a guide, which is rigidly connected to the fixed clamping jaw. The necessary manufacturing demands are here also relatively high; the construction of the wrench causes a certain malfunctioning from build-up of dirt and/or wear. The wrench cannot be simply pulled off, gripping by hand is necessary near the bolt head to move the mobile jaws. This applies particularly also during the placement of the wrench (on the workpiece). Employment is therefore only possible when the wrench head is accessible.
This known wrench is not self-clamping since the moveable clamping jaw rests against a stop surface in its terminal position. The wrench does therefore not fulfill the requirement mentioned in the beginning.
Wrenches that have toothed clamping jaws (U.S. Pat. No. 4,616,534, DE-A 196 12 759) may be ratchet-operated in small increments because of the teeth; the engagement of teeth on the workpiece may, however, lead to damages so that these wrenches cannot be employed in the industrial area or on sensitive workpieces, for instance in the bolting operation in plumbing.
On a known wrench of the type mentioned in the beginning (U.S. Pat. No. 1,735,257), the clamping surface on the moveable clamping jaw, with which the clamping force is exerted onto the workpiece, is designed with a flat surface. The opposed clamping surface of the fixed clamping surface is convex arcuated. With this wrench, the bolting process may be performed only by ratcheting movements of 60xc2x0.
It is therefore the object of the invention to design an open-end wrench of the type mentioned in the beginning that has essentially the function of a rigid open-end wrench but which is self-clamping, and which makes possible ratchet movements of 30xc2x0 whereby the necessary swiveling movement of the wrench handle does not substantially amount to more than 30xc2x0 itself.
It is therefore the object of the invention to design an open-end wrench of the type mentioned in the beginning that has essentially the function of a rigid open-end wrench but which is self-clamping and which makes possible ratchet movements of 30xc2x0 whereby the necessary swiveling movement of the wrench handle itself does not substantially amount to more than 30xc2x0.
This object is achieved according to the invention in that each clamping surface is subdivided by at least two convex arcuated clamping teeth; that a recess, which recoils opposite the plane of the clamping surface, is connected on the side of the handle to the clamping surface of the fixed jaw, and that the moveable clamping jaw is provided with a recess in the area behind the clamping surface and the pivot point and which recess approximately corresponds to the recess behind the fixed clamping jaw in the open position of the wrench.
As a result of its self-clamping function, the wrench adjusts itself to the dimensions of the workpiece so that especially the deviation derived from the tolerance is compensated and does not lead to the danger of slipping. The widening of the mouth of the wrench is also compensated by the self-clamping effect and this does not lead therefore to possible slipping. Only one single wrench is necessary for nominal widths in the metric and inch-system whereby the amount of the required wrench assortment is decreased.
The self-clamping effect makes also possible to leave the wrench on the workpiece in a self-clamping manner if said wrench has to be released because of a necessary intermediate operational step. The wrench does also not fall down when released during work overhead.
The wrench may be ratchet-operated in increments of 30xc2x0 so that it does not have to be pulled off and slipped on anew. The time in handling is thereby decreased considerably.
Only by the provided recess behind the clamping surfaces of the two clamping jaws has it been made possible to manipulate the self-clamping wrench in a ratcheting movement since only through these recesses enough space has been created to move the wrench back over the workpiece only with minute widening of the wrench mouth. The swiveling motion of the wrench handle, as performed during ratcheting action of approximately 30xc2x0, is only a little more than 30xc2x0. The wrench can therefore be employed also under very tight working conditions. Nevertheless, the wrench has substantially the shape and dimensions of a rigid open-end wrench and may be handled just as simple.
According to one embodiment of the invention it is proposed that the moveable clamping jaw protrude with one joint eye into the longitudinal slot that runs from the fixed clamping jaw into the wrench handle. Thereby the parts moving relatively to one another are arranged in a way to be protected so that there is achieved a smooth and compact design of the wrench. The spring, which communicates with the moveable clamping jaw, is preferably a tension spring that is braced against the wrench handle and which pushes the moveable clamping jaw in the direction of its clamping position. This tension spring is preferably a leaf spring attached to the wrench handle whereby said spring is mainly arranged in the longitudinal slot and whereby it does not interfere with the handling of the wrench and cannot be damaged.
If the center segment of the leaf spring does protrude from the longitudinal slot in the open position of the wrench, then the moveable clamping jaw can be moved by applying pressure on this center segment.
According to a preferred embodiment of the invention, it is proposed that the moveable clamping jaw is provided with a stop surface that is angled relative to the clamping surface and which connects to the clamping surface on the handle side. This stop surface prevents that the wrench embraces the workpiece too far when slipped on and after each ratcheting action.